566 Prof. Rutherford and Mr. Soddy on 



The ethylene bath was cooled by liquid air slightly below 

 the temperature of condensation, and a definite volume of the 

 emanation was sent into the apparatus from B, and conveyed 

 by a very slow gas-stream for 10 minutes into the spiral so 

 that it was condensed near the beginning of the spiral. The 

 current of gas to be employed is then adjusted and the tempe- 

 rature of the bath allowed to rise slowly. One observer took 

 the determinations of the temperature and the lapse of time, 

 the other the readings of the electrometer. The temperature 

 at which the electrometer-needle commenced to move was 

 recorded, and the rate of movement at succeeding tem- 

 peratures. In most of the experiments the temperature rose 

 at a rate of about 1°'6 to 2° per minute. 



The following table gives an illustration of the results 



obtained : — 



m Divisions per second of 



Temperature. +1 , *\ , 



r the electrometer. 



-160° 



-156° 



-154 c -3 1 



-153°-8 21 



-152°-5 24 



The observed temperature of the first appearance of the 

 emanation is subject to a correction for the time taken for 

 the emanation to be swept into the testing-vessel after 

 volatilization, This depends on the volume of the spiral and 

 its temperature, and on the current of gas, and can be 

 approximately calculated for each experiment. Knowing the 

 rate of rise of temperature in the experiment the actual 

 temperature at which volatilization commenced could be 

 deduced. In the table given above for a gas-stream of 

 1*38 cms. per second the application of this correction lowers 

 the temperature of volatilization about o, 8 C. The following- 

 table includes some of the corrected results for the radium 

 emanation . Under the column T 2 the temperatures at which the 

 emanation began to volatilize are given, under T 2 the tempera- 

 tures at which one half of the total amount had been given off. 

 Gas. 

 Hydrogen. 



Oxygen 



c. c. per second. 



T r 



T 2 . 



. -25 



-151-3 



-150 



•32 



-153-7 



-151 



•33 



-153-7 



-151 



•92 



-152 



-151 



1-38 



-154 



-153 



2-3 



— 162-5 



-162 



. -34 



-152-5 



-151-5 



•33 



-152-5 



-151-5 



•58 



— 155 



-153 



